Here's a brief history lesson from The New Yorker's Book Bench blog about how little blonde girls came to be "indelibly equated with innocence" who redeem sinful adults through sacrificial deaths, inspired by one of the most telling racist Hunger Games tweets: "Awkward moment when Rue is some black girl and not the little blonde innocent girl you picture."
So how come we prefer to make martyrs out of innocent blonde girls, or even Virgin Suicides-like nymphets? Naturally, it all starts with the Christ child, who inspired some of the nineteenth-century writers so preoccupied with "doomed child saviors," like Harriet Beecher Stowe's Little Eva and Charles Dickens' Little Nell.
The Book Bench's Maria Tatar says this persistent obsession filters into real life, too:
The deaths of blonde girls and women have a way of monopolizing the media limelight, as the frenzied press coverage of Jon-Benet Ramsey and Natalie Holloway makes all too clear. Their murders are emphasized far more than the deaths of "some black girl" (that "some" packs a dehumanizing punch) or, for that matter, anyone living below the poverty line without a halo of blonde hair.
Tatar argues that Suzanne Collins "enlarges the myth about girl saviors to include multiple ethnic identities" in the the Hunger Games novels because it's (Spoiler Alert!) dark-skinned Rue, not Katniss' sister Prim, Rue's pale doppelganger, that dies in the first book. Her death "is a murder, one pictured with unsentimental candor in the movie" that inspires Katniss to salute the residents of Rue's home, District 11, provoking them into rebellion — her death isn't a catalyst for redemption, but for radical change.
However! Tartar fails to note that (Double Spoiler Alert!!) Prim does die in Mockingjay, the last book in the series, while in the middle of what is basically the most saintly act ever: delivering supplies to frightened children who are even more innocent than she. Prim's death doesn't inspire Katniss, but rather scars her to the point of mental instability. Rue is not as pure and blameless: in the movie, she inspires Katniss to drop a deadly hive onto the other tributes, and she would have definitely killed, say, Cato, if she got the chance. Prim, on the other hand — perhaps because she falls into the still-prevalent innocent blonde trope — dies a more sentimental, gentle death.
Little, Blonde, Innocent, and Dead [New Yorker]